I am a male INFJ, between the age of 30 and 35. I will not give you my exact real age.
Still grinning about this.
But as for everything else, I'm put off by the idea of calculating an approach to someone based on their perceived — or even known — MBTI. I'm serious about this. Any time anyone has approached me using some sort of preconceived label has been immediately offensive, even if they don't tell me. Wrong approach, man, please don't do it if you respect her or yourself.
If you really want a set of guidelines for such things, read
The Game, or anything else by Neil Strauss. I hate the book and find Neil Strauss to be a class-A creep, but a lot of guys swear by it for dating obviously sexually attractive women. Go for it.
My ENTP long-time friend (since 5th grade—going on 18 years now) is hardcore. The girl you're talking about is going to be tough if she's anything like her. For my friend, should she find you cute, she'd offer you a fling and nothing more. Relationships for her are really hard to manage because she thinks fast, will knock the ground out from under you on most subjects, and has little or no time for any insecurities. She's a very weird mix, a complete tomboy but loves the girliest shades of purple. I'm pretty sure she could kill a man in three seconds flat with her training, though, so when I say "man-killer," it's literal.
I have an ENTP brother, too. Totally nuts. With my personality type, ENTPs are fantastic friends and siblings—entertaining, hilarious, and engaging. But as partners? Eh, I'm open to it, but I haven't been attracted to one yet. Again, this has nothing to do with me applying a Type to them.
To end this, I'll echo what others said; just get some balls and ask her out, or get to know her better. There's no hope of anything unless you do that. Concentrate on WHO SHE IS, not her MBTI, looks, or any other stereotype. She's going to be far more complex than any acronym can do justice.
Final words: infatuation is stupid.